Conventionally, a method is known for having a slot antenna built into a semiconductor package in which a semiconductor chip is mounted on an interposer. Moreover, in order to add a shielding function to the semiconductor package, a technique for implementing a module with a built-in antenna has been proposed in which the surface of an sealing resin for sealing the semiconductor chip is covered using a conductive film; an opening is formed that extends from the conductive film for shielding to a conductive layer of the interposer; and the opening is made to function as a slot antenna.
A slot antenna of the interposer is formed as an opening in a conductor pattern of a conductor layer. Since the shape of the conductor pattern is such that the opening is included therein, it becomes necessary to secure a relatively large space. In the case of forming a slot antenna in an interposer having a plurality of conductor layers, in the areas in which the slot antenna is to be formed, there occur differences in the metal coverage rates of the conductor layers thereby making the interposer susceptible to warpage. Particularly, an interposer is manufactured by arranging a number of interposers on a single substrate. Thus, the warpage occurring in the individual interposers gets accumulated, and the entire interposer tends to have a large warpage. For that reason, there are times when defects occur during the reflow process for mounting components on the interposer, during the resin sealing process or the dicing process in the semiconductor package manufacturing, and the reflow process for mounting the semiconductor package on the mounting interposer. Hence, there has been a demand for effectively reducing the warpage of the interposer.